The preservation of food is important for commercial as well as health reasons. An increase in the shelf life of food products simplifies delivery and handling systems and increases profit for the producer and quality for the consumer. Various synthetic additives have long been employed to preserve, or otherwise increase the shelf life of food products.
Chemical additives in foods are subject to ever increasing regulation and many additives which were previously permitted to be used in foods are now restricted. Furthermore, the consumer demand for additive-free food is steadily increasing. As a result of the foregoing, there is a significant and rapidly growing demand for methods and means for the preservation of food products, which do not rely upon the introduction of any additives into those food products.
One significant approach to the problem of food preservation relies upon the use of preservative agents which are disposed in the food package separate from the food product itself. Toward this end it is known to include preservative agents such as oxygen scavengers, desiccants, odor absorbents, carbon dioxide scavengers, or biocides in a permeable package which is disposed within the food container. The preservative agent acts to create an atmosphere which is conducive to increased shelf life of the food. For example, it is known to seal oxygen absorbing materials, such as iron compounds, into oxygen permeable packages and to include such packages in sealed food containers. Presence of the package of oxygen scavenging material creates a very low oxygen atmosphere in the food container thereby greatly retarding spoilage of the food. Preservative compositions and packages for those compositions are disclosed in U.S. Pat. Nos. 4,421,235; 4,332,845; 4,579,223; 4,657,133; 4,667,814; 4,769,175 and 4,856,649.
In order to function properly, the package containing the preservative agent must be sufficiently porous to allow atmospheric gases to pass therethrough, but at the same time must be of a porosity sufficiently fine so as to retain the preservative agent therein. One problem which significantly inhibits the function of additive packages of this type is the clogging of the pores by oil, grease or water present in the food products. Such materials can form an adherent layer upon the package which presents an effective barrier to contact between the preservative agent and the gaseous atmosphere in the food container.
One approach to the problem is disclosed in U.S. Pat. No. 4,856,650. Detailed therein is a process whereby an air permeable sheet is coated with a layer of fluorocarbon polymer which is then laminated onto the sheet by a hot pressing operation. Despite this invention, there is still a need for a preservative package having a higher degree of resistance to clogging by oils and aqueous based materials.
The present invention provides a significant improvement in preservative packages of this type insofar as it enables the fabrication of food preservative packages which actually repel water and oil. Preservative packages made in accordance with the present invention exhibit a porous structure having an actual conformal coating of a fluoroacrylate based polymer thereupon and because of this, they are not coated or clogged by oils or other liquids and hence retain a high level of activity. These and other advantages of the present invention will be readily apparent from the drawings, discussion and description which follow.